Macro- and micro-nutrients and their bioavailability in polish herbal medicaments

Abstract

Several polish herbal medicaments were studied to determine trace elements and their bioavailable forms by the use of the ICP-AES method. The contents of Al, B, Ba, Bi, Ca, Cd, Cr, Cu, Fe, Mg, Mn, Ni, P, Pb, Se, Si, Ti, V and Zn were determined. The total concentrations were measured in samples mineralised with concentrated nitric acid and hydrogen peroxide in a microwave system. The one-step extraction was applied, using, as extractants: deionised water, diluted hydrochloric acid and buffer solution containing pepsin. Efficiencies of the leaching versus time were investigated. The extraction efficiencies were analysed, taking into account bioavailability of elements under conditions simulating digestion processes in the alimentary system. The contents of the examined elements in prescribed amounts of medication, were compared to the nutritional requirements and daily permissible dose. The results are considered in terms of the utility of the natural herbal medicaments as a source of minerals indispensable for proper functioning of the human organism. Some points of merit (precision of measurements, accuracy by Standard Reference Material analysis) are also considered.

Introduction

The trace elements, together with other essential nutrients, are necessary for growth, normal physiological functioning, and maintaining of life; they must be supplied by food, since the body cannot synthesis them. The exact classification of trace versus macro minerals is not clear cut, but traces are often considered as minerals required by the body in amounts less than 100 mg daily. While some of them are vitally important for health, the roles of others are unclear. Recommended intakes have been set for some trace elements and their deficiency can lead to disease, but a lack of others does not cause any recognised problems. To decide whether a micro-nutrient is “essential” or not, several criteria are used, such as the presence of the nutrient in healthy tissue, if it appears in the fetus and newborns and if the body maintains homeostatic control over its uptake in the bloodstream or tissue and its excretion. The following are considered essential micro-nutrients: cobalt, copper, chromium, fluorine, iron, iodine, manganese, molybdenum, selenium and zinc. On the other hand, nickel, tin, vanadium, silicon and boron have recently been found to be important micro-nutrients, whereas aluminium, arsenic, barium, bismuth, bromine, cadmium, germanium, gold, lead, lithium, mercury, rubidium, silver, strontium, titanium and zirconium are all found in plant and animal tissue, yet their importance is still being determined. The nutritionally essential values and toxicity values have also been examined and widely discussed (Goldhaber, 2003; The Columbia Encyclopedia, 2001–2004). Reference Doses set by The US Environmental Protection Agency, Acceptable Daily Intakes calculated by The World Health Organisation, Dietary Reference Intakes established by The US Food and Nutrition Board of the Institute of Medicine and Reference Daily Intakes examined by The US Food and Drug Administration enable evaluation of foods as a micro-nutrient sources.

Based on the World Health Organization definitions (WHO, 1991), Herbal medicines are plant-derived materials and preparations with therapeutic or other human health benefits, which contain either raw or processed ingredients from one or more plants, inorganic materials or of animal origin. Herbal medicines have been used for hundreds of years and recognised as a valuable and readily available resource for health in nations all over the world. In recent years, herbal medicine has been increasingly used by the general public on a self-selection basis, to either replace or complement conventional medicine therapies. A World Health Organization survey indicated that about 70–80% of the world population, especially in developing countries, rely on non-conventional medicine, mainly from herbal sources in their primary healthcare (Akerele, 1993). Botanical product consumption is expected to grow exponentially. The distinct need to study herbal medicines scientifically is obvious. With significant advances in preclinical and clinical research, there are now several paths to achieve a knowledge base on the composition (chemical features) and pharmacological properties of specific herbs and medicines.

Quality control monitoring ensures safety, efficacy and quality of herbal medicines and their preparations. Therefore, quality control consists of a regular check of the quality of herbal medicines, and is performed according to the specifications of the product which detail the requirements for identity, purity and content of characterising compounds (Benthin et al., 1999, Guo et al., 2001). Also, contents of undesirable components, such as herbicides, pesticides, heavy metals, alfatoxins, micro-organisms, mycotoxins, insects and undeclared herbal constituents, should be verified in medicinal plant raw materials and herbal remedies. Trace elements have both a curative and a preventive role in combating diseases. It is very important to know the level of macro- and micro-elements in medicinal plants and herbal medicaments and to estimate their role as sources of these components in the human diet because, at elevated levels, these metals can also be dangerous and toxic. These precautions are indispensable when larger amounts of the products are consumed, i.e. when recommended dosages are followed and long-term therapy is undertaken.

Many studies have been performed on active herbal plant constituents and their activity (for example, Chen et al., 2003, De Mastro et al., 2004, Dragland et al., 2003, Lee et al., 2004, Mannila et al., 2003, Oreopoulou, 2003). Several attempts have been made to determine of the macro- and micro-nutrient contents of herbal, medicinal and aromatic plants from many countries all over the world. For example medicinal, aromatic and spice plants growing in Argentina (Scarpa, 2004), Austria (Chizzola, Michitsch, & Franz, 2003), Egypt (Abou-Arab, Kawther, El Tantawy, Badeaa, & Khayria, 1999), Hungary and Germany (Lemberkovics, Czinner, Szentmihályi, Balázs, & Szöke, 2002), India (Kumar et al., 2005, Naidu et al., 1999, Rajurkar and Damame, 1997), Nigeria (Ajasa, Bello, Ibrahim, Ogunwande, & Olawore, 2004), Poland (Lemberkovics et al., 2002, Łozak et al., 2002, Solecki et al., 2003), Serbia (Ražić, Onjia, & Potkonjak, 2003), Spain (Garcia et al., 2000, López et al., 2000) and the USA (Kumar et al., 2005) were monitored. As far as herbal remedy chemical composition is concerned, especially for traditional Indian and Chinese remedies (see for example, Ernst, 2002, Li and Deng, 2003, Wang et al., 1996, Yang et al., 2004), the data for European medicines are still missing. It is also very important to estimate mineral bioavailability. The amount of HCl-extractable minerals indicates their availability from foods. Extractable minerals are those which are soluble in diluted HCl, the acid found in human stomach (Duhan, Khetarpaul, & Bishnoi, 2004). Digestion, using simulated gastric and intestinal fluid, also provides useful information on mineral bioavailability (Elless, Blaylock, Huang, & Gussman, 2000). In the case of herbs, fractionation of the macro- and micro-nutrients was performed only by quantitative determination of the elements in plant materials and plant infusions (see Fernández et al., 2002, Łozak et al., 2002). As far as we know, no such studies on herbal remedies have been undertaken. Also, to the best of our knowledge, enzymatic extraction has not been applied to the herbal medicaments. Enzymatic hydrolysis procedures were employed for the biological samples, e.g., for human hair and mussel (Bermejo-Barrera, Fernández-Nocelo, Moreda-Piñeiro, & Bermejo-Barrera, 1999), selenium enriched onion, garlic and yeast (Ponce de Leon, Sutton, Caruso, & Uden, 2000), bovine milk (Silva, Lopes, Nóbrega, Souza, & Nogueira, 2001), selenised mushroom (Dernovics, Stefánka, & Fodor, 2002) and Indian mustard (Brasicca juncea) (Elless et al., 2000).

The objectives of this study were to determine the total contents of the macro- and micro-elements in commercial herbal drugs, to estimate amounts of the micro-nutrients provided by herbal medicine consumption and to verify essential-nutrient intake by the extraction investigation under conditions simulating food digestion in the stomach.